EP2686359B1 - Polyurethane coating material composition, multistage coating methods using these coating material compositions, and also the use of the coating material composition as clearcoat material and pigmented coating material, and application of the coating method for automotive refinish and/or for the coating of plastics substrates and/or of utility vehicles - Google Patents

Description

The present invention relates to coating compositions comprising at least one polyhydroxyl-containing compound (A), at least one polyisocyanate-group-containing compound (B) and at least one catalyst (D) based on a zinc-amidine complex.

The present invention furthermore relates to multistage coating processes using these coating compositions and to the use of the coating compositions as a clearcoat or application of the coating process for automotive refinishing and / or for the coating of plastic substrates and / or commercial vehicles.

Polyurethane coating compositions usually contain a catalyst, wherein in addition to acidic compounds in particular tertiary amines and / - or metal compounds, such as various tin compounds, in particular dibutyltin dilaurate and dibutyltin oxide are used.

The use of tin-containing catalysts is due to the many tin compounds inherent toxicity in coating materials to avoid. From the "Working Group on Classification and Labeling" of the European Commission dibutyltin oxide (DBTO) and dibutyltin dilaurate (DBTL) were categorized accordingly.

The article "Catalysis of the Isocyanate-Hydroxyl Reaction by Non-Tin Catalysts" available from the Internet at the address www.wernerblank.com by Werner J. Blank, Z.A. Hey and Ed. T. Hessell of King Industries Inc. therefore alternatives to the usual tin-containing catalysts based on various metal salts and metal complexes, such as zirconium chelates, aluminum chelate and bismuth carboxylate, are described.

From the DE 10 2008 061 329 A1 coating compositions are known in which the use of metal-containing catalysts should be avoided as far as possible and which instead contain 1,3-substituted imidazolium salts as a catalyst for deblocking blocked polyisocyanates in polyurethane coating compositions.

The WO04 / 029121 describes polyurethane compositions which are stabilized by the addition of acids having a pKa range of between 2.8 and 4.5 with respect to the reactivity of the composition, which acids can be used simultaneously as a catalyst. Examples of acids having a pKa range between 2.8 and 4.5 are benzoic acid, hydroxybenzoic acid, salicylic acid, phthalic acid and the like. used. The compositions preferably contain no further catalyst, but it is also additionally possible to use the customary known polyurethane catalysts, such as tertiary amines or amidines or organometallic compounds, in particular tin compounds. When amines are used as the catalyst, great care must be taken in selecting the type of amine and its amount, as the amine catalysts can in part eliminate the stabilizing effect of the added organic acids.

In the US patent US 5,847,044 polyurethane powder coatings are described which contain as catalysts N, N, N'-trisubstituted amidines, especially bicyclic amidines.

The WO 09/135600 describes polyurethane compositions, in particular sealants, adhesives and foams containing as catalyst the reaction product of a metal salt with nitrogen-containing, heterocyclic compounds, in particular substituted imidazoles.

The DE-A-24 34 185 describes a process for the preparation of amidine-metal complexes and their use as catalysts for the isocyanate polyaddition reaction. The amidine-metal complexes are prepared by reacting an amidine with a 0.5 to 4-fold molar amount of a metal compound, wherein as amidines both monocyclic and / or bicyclic compounds, in particular imidazoles, as well as acyclic compounds, such as formamidines , Acetamidines, benzamidines and guanidines. The metal compounds used are those of trivalent iron, of divalent nickel, of divalent zinc, of divalent manganese, of bivalent tin or of tetravalent tin, in particular using the corresponding carboxylates.

Finally, describe the US patent US Pat. No. 7,485,729 B2 as well as the equivalent writings WO06 / 022899 . US 2006/0247341 A1 and US 2009/0011124 A1 Organo-metal compounds and coating compositions containing them. The coating compositions are powder coatings based on hydroxyl-containing polyacrylates or polyesters and polyisocyanates containing uretdione groups, liquid coatings based on hydroxyl-containing polyacrylates or polyesters and blocked Polyisocyanates and solvent-based coating compositions based on epoxy / carboxy or epoxy / anhydride components described. The organometallic compounds used as the catalyst, in addition to other metal amidine complexes, are cyclic or acyclic zinc biscarboxylate bis-amidine complexes such as Zn (1,1,3,3-tetramethylguanidine) ₂ (2-ethylhexanoate) ₂ .

task

It is an object of the present invention, therefore, to provide coating compositions, in particular for automotive refinishing and commercial vehicle coating, which ensure good assembly stability after only a very short time, that is to say that they cure rapidly even under the conditions of refinishing and painting Should ensure painting of commercial vehicles, so far hardened after curing for 30 min at 60 ° C that first assembly work or unmasking can be performed without damaging the coating. At the same time, however, the coating compositions should have a good potlife of at least 2 hours at room temperature and after mixing the binder component with the isocyanate component. By pot life is meant the period of time within which the coating composition has reached twice its initial viscosity. In addition, the coating compositions should result in coatings with good through-cure and sufficient final hardness. Furthermore, these coating compositions should show no color changes before and after curing. Particularly in the field of clearcoats in the automotive industry, there are high demands on the intrinsic color of the systems. Thus, the catalyst may neither have a natural color, nor may it lead to the usual paint components to a discoloration in the mixing or curing of the paint.

Furthermore, it should be possible to add the catalyst to the coating system from the outset. However, the incorporation of the catalyst into the coating systems should not adversely affect the storage stability of the coating composition from the beginning. In addition, the catalyst should be insensitive to hydrolysis, since even in organically dissolved systems, the usually high concentration of hydroxyl groups can lead to a reduction of the catalyst activity over the storage time. Particularly in the field of automotive refinish, an extremely high storage stability is also advantageous at higher temperatures.

Finally, the coating compositions should be simple and very easy to produce reproducible and prepare during the paint application no environmental problems. In particular, tin-containing catalysts should be avoided or at best dispensable altogether.

Solution of the task

wobei R₅ = Wasserstoff und R₁, R₂, R₃, und R₄ jeweils gleiche oder verschiedene Reste sind, wobei R₁ und R₃ Wasserstoff oder ein Alkylrest oder ein Arylrest sind und R₂ und R₄ ein Alkylrest oder ein Arylrest sind, und
mindestens eine monomere aromatische ggf. substituierte Carbonsäure (S), deren Carboxylgruppe in Konjugation zu einem π-Elektronensystem steht,In light of the above problem, a coating composition was found containing at least one polyhydroxyl group-containing compound (A), at least one polyisocyanate group-containing compound (B) having free and / or blocked isocyanate groups, at least one catalyst (D) based on a zinc amidine Complex which can be prepared by reacting 1.0 mole of one or more zinc (II) biscarboxylates with more than 2.0 moles of an amidine of the formula (I) or with more than 2.0 moles of a mixture of two or more amidines of the formula (I)

wherein R ₅ = hydrogen and R ₁ , R ₂ , R ₃ , and R _{4 are} each the same or different radicals, wherein R ₁ and R _{3 are} hydrogen or an alkyl radical or an aryl radical and R ₂ and R _{4 is} an alkyl radical or an aryl radical are and
at least one monomeric, optionally substituted, carboxylic acid (S) whose carboxyl group is conjugated to a π-electron system,

The present invention furthermore relates to multistage coating processes using these coating compositions and to the use of the coating compositions as a clearcoat or application of the coating process for automotive refinishing and / or for the coating of plastic substrates and / or commercial vehicles.

It is surprising and was unpredictable that the coating compositions ensure good assembly stability even after a very short time, even under the conditions for automotive refinish, ie that they ensure rapid curing even under the conditions of refinishing, ie already after curing for 15 minutes 60 ° C are tack-free. At the same time, however, the coating compositions exhibit a good potlife of at least 2 hours at room temperature and after mixing the binder component with the isocyanate component. By pot life is meant the period of time within which the coating composition has reached twice its initial viscosity.

In addition, the coating compositions provide coatings having good through cure and sufficient final hardness. Furthermore, the catalyst neither shows its own color, nor does it lead to the usual paint components to a discoloration in the mixing or curing of the paint.

Furthermore, the catalyst can be added to the coating system from the outset, without adversely affecting the storage stability of the coating compositions. In addition, the catalyst is insensitive to hydrolysis, so that the usually high concentration of hydroxyl groups, even in organically dissolved systems, does not lead to a reduction in the catalyst activity over the storage time, which is particularly advantageous in the field of automotive refinish.

Finally, the coating compositions are simple and very easy to produce reproducible and prepare during the paint application no environmental problems. In particular, tin-containing catalysts can be avoided or are even completely dispensable at best.

The polyhydroxyl group-containing compound (A)

As polyhydroxyl-containing compound (A), it is possible to use all compounds known to the person skilled in the art which have at least 2 hydroxyl groups per molecule and are oligomeric and / or polymeric. It is also possible to use mixtures of different oligomeric and / or polymeric polyols as component (A).

The preferred oligomeric and / or polymeric polyols (A) have mass-average molecular weights Mw> 500 daltons, measured by gel permeation chromatography (GPC) against a polystyrene standard, preferably between 800 and 100,000 daltons, in particular between 1,000 and 50,000 daltons.

Particular preference is given to polyester polyols, polyurethane polyols, polysiloxane polyols, polyacrylate polyols and / or polymethacrylate polyols and their copolymers, referred to below as polyacrylate polyols.

The polyols preferably have an OH number of 30 to 400 mg KOH / g, in particular between 100 and 300 KOH / g. The hydroxyl number (OH number) indicates how many mg of potassium hydroxide are equivalent to the amount of acetic acid bound by 1 g of substance in the acetylation. The sample is boiled in the determination with acetic anhydride-pyridine and the resulting acid is titrated with potassium hydroxide solution (DIN 53240-2). In the case of pure poly (meth) acrylates, the OH number can also be determined sufficiently accurately by calculation based on the OH-functional monomers used.

The glass transition temperatures, measured by means of DSC measurements according to DIN-EN-ISO 11357-2, of the polyols are preferably between -150 and 100 ° C., more preferably between -120 ° C. and 80 ° C.

Suitable polyester polyols are, for example, in EP-A-0 994 117 and EP-A-1 273 640 described. Polyurethane polyols are preferably prepared by reacting polyesterpolyol prepolymers with suitable di- or polyisocyanates and are described, for example, in US Pat EP-A-1 273 640 described. Suitable polysiloxane polyols are for example in the WO-A-01/09260 described, wherein the polysiloxane polyols listed there may be used preferably in combination with other polyols, especially those having higher glass transition temperatures.

Most preferably, component (A) contains one or more polyacrylate polyols and / or polymethacrylate polyols. Together with the or the polyacrylate polyols and / or polymethacrylate polyols, it is possible to use further oligomeric and / or polymeric polyhydroxyl-containing compounds, for example polyester polyols, polyurethane polyols and polysiloxane polyols, in particular polyester polyols.

The poly (meth) acrylate polyols very particularly preferred according to the invention are generally copolymers and preferably have mass-average molecular weights Mw between 1000 and 20,000 daltons, in particular between 1,500 and 10,000 daltons, in each case measured by gel permeation chromatography (GPC) against a polystyrene standard.

The glass transition temperature of the copolymers is generally between -100 and 100 ° C, in particular between -50 and 80 ° C (measured by DSC measurements according to DIN-EN-ISO 11357-2).

The poly (meth) acrylate polyols preferably have an OH number of 60 to 250 mg KOH / g, in particular between 70 and 200 KOH / g, and an acid number between 0 and 30 mg KOH / g.

The hydroxyl number (OH number) is determined as described above (DIN 53240-2). The acid number indicates the number of mg of potassium hydroxide which is used to neutralize 1 g of the respective compound (DIN EN ISO 2114).

Preferred hydroxyl-containing monomer building blocks are hydroxyalkyl acrylates and / or hydroxyalkyl methacrylates, in particular 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 3-hydroxybutyl acrylate, 3-hydroxybutyl methacrylate and in particular 4-hydroxybutyl acrylate and / or 4-hydroxybutyl methacrylate used.

Other monomer building blocks used for the poly (meth) acrylate polyols are preferably alkyl acrylates and / or alkyl methacrylates, such as preferably ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, butyl acrylate, butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, amyl acrylate , Amyl methacrylate, hexyl acrylate, hexyl methacrylate, ethylhexyl acrylate, ethylhexyl methacrylate, 3,3,5-trimethylhexyl acrylate, 3,3,5-trimethylhexyl methacrylate, stearyl acrylate, stearyl methacrylate, lauryl acrylate or lauryl methacrylate, cycloalkyl acrylates and / or cycloalkyl methacrylates such as cyclopentyl acrylate, cyclopentyl methacrylate, isobornyl acrylate, isobornyl methacrylate or in particular cyclohexyl acrylate and / or cyclohexyl methacrylate.

As further monomer building blocks for the poly (meth) acrylate polyols it is possible to use vinylaromatic hydrocarbons, such as vinyltoluene, alpha-methylstyrene or, in particular, styrene, amides or nitriles of acrylic or methacrylic acid, vinyl esters or vinyl ethers, and in minor amounts, in particular acrylic and / or methacrylic acid ,

The polyisocyanate group-containing compounds (B)

Suitable components (B) are per se known substituted or unsubstituted aromatic, aliphatic, cycloaliphatic and / or heterocyclic polyisocyanates. Examples of preferred polyisocyanates are: 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, p-phenylene diisocyanate, biphenyl diisocyanates, 3,3'-dimethyl-4 , 4'-diphenylene diisocyanate, tetramethylene-1,4-diisocyanate, hexamethylene-1,6-diisocyanate, 2,2,4-trimethylhexane-1,6-diisocyanate, isophorone diisocyanate, ethylene diisocyanate, 1,12-dodecane diisocyanate, Cyclobutane-1,3-diisocyanate, cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, methylcyclohexyl diisocyanate, hexahydrotoluene-2,4-diisocyanate, hexahydrotoluene-2,6-diisocyanate, hexahydrophenylene-1,3-diisocyanate, Hexahydrophenylene-1,4-diisocyanate, perhydrodiphenylmethane-2,4'-diisocyanate, 4,4'-methylenedicyclohexyl diisocyanate (eg Desmodur® W from Bayer AG), tetramethylxylyl diisocyanates (eg TMXDI® from American Cyanamid) and mixtures of the abovementioned polyisocyanates. Preferred polyisocyanates are also the biuret dimers and the isocyanurate trimers of the aforementioned diisocyanates. Particularly preferred polyisocyanates (B) are hexamethylene-1,6-diisocyanate, isophorone diisocyanate and 4,4'-methylenedicyclohexyl diisocyanate, their biuret dimers and / or their isocyanurate trimers and / or their asymmetric trimers, such as, for example: commercially available under the designation Desmodur® N3900 asymmetric HDI trimer.

In a further embodiment of the invention, the polyisocyanates are polyisocyanate prepolymers having urethane structural units which are obtained by reacting polyols with a stoichiometric excess of the aforementioned polyisocyanates. Such polyisocyanate prepolymers are, for example, in US-A-4, 598,131 described.

The polyisocyanate group-containing component (B) may be present in a suitable solvent (L). Suitable solvents (L) are those which provide sufficient solubility of the polyisocyanate component and are free of isocyanate-reactive groups. Examples of such solvents are acetone, methyl ethyl ketone, cyclohexanone, methyl isobutyl ketone, methyl isoamyl ketone, diisobutyl ketone, ethyl acetate, n-butyl acetate, ethylene glycol diacetate, butyrolactone, diethyl carbonate, propylene carbonate, ethylene carbonate, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, N Ethylpyrrolidone, methylal, butylal, 1,3-dioxolane, Glycerol formal, benzene, toluene, xylene, n-hexane, cyclohexane, Solventnaphtha®, 2-methoxypropylacetate (MPA), and ethylethoxypropionate.

Hydroxyl-containing compounds (C)

The coating compositions according to the invention may optionally contain, in addition to the polyhydroxyl-containing component (A), one or more monomeric hydroxyl-containing compounds (C) other than component (A). These compounds (C) preferably contain from 0 to 20% by weight, more preferably from 1 to 10% by weight, very preferably from 1 to 5% by weight, based in each case on the binder content of the coating composition ,

As hydroxyl-containing compound (C) low molecular weight polyols are used.

As low molecular weight polyols, for example, diols, such as preferably ethylene glycol, neopentyl glycol, 1,2-propanediol, 2,2-dimethyl-1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 1.5, - Pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol and 1,2-cyclohexanedimethanol, as well as polyols, such as preferably trimethylolethane, trimethylolpropane, trimethylolhexane, 1,2,4 Butantriol, pentaerythritol and dipentaerythritol. Preferably, such low molecular weight polyols are added in minor proportions of the polyol component (A).

Catalyst (D)

It is essential to the invention that the coating composition comprises at least one catalyst (D) based on a zinc amidine complex which can be prepared by reacting 1.0 mole of one or more zinc (II) biscarboxylates with more than 2.0 moles of one

wobei R₅ = Wasserstoff und R₁, R₂, R₃, und R₄ jeweils gleiche oder verschiedene Reste sind, wobei R₁ und R₃ Wasserstoff oder ein Alkylrest oder ein Arylrest sind und R₂ und R₄ ein Alkylrest oder ein Arylrest sind.Amidines of the formula (I) or containing more than 2.0 moles of a mixture of two or more amidines of the formula (I)

wherein R ₅ = hydrogen and R ₁ , R ₂ , R ₃ , and R _{4 are} each the same or different radicals, wherein R ₁ and R _{3 are} hydrogen or an alkyl radical or an aryl radical and R ₂ and R _{4 is} an alkyl radical or an aryl radical are.

Preferably, the zinc-amidine complex can be prepared either by reacting 1.0 mol of one or more zinc (II) biscarboxylates having at least 2.5, more preferably at least 3.0, and most preferably from 3.0 to 4.0 Moles, of an amidine of the formula (I) or preparable by reacting 1.0 mol of one or more zinc (II) biscarboxylates with at least 2.5, particularly preferably with at least 3.0 and very particularly preferably with 3.0 to 4, 0 moles, a mixture of two or more amidines of the formula (I).

The catalyst (D) is particularly preferably preparable by reacting 1.0 mol of a zinc (II) biscarboxylate with at least 2.5, particularly preferably with at least 3.0 and very particularly preferably with 3.0 to 4.0 mol of an amidine of the formula (I).

The radicals R ₂ and R ₄ are preferably identical or different acyclic, straight-chain or branched alkyl radicals and / or identical or different aryl radicals. The radicals R ₁ and R ₃ are preferably hydrogen or identical or different acyclic, straight-chain or branched Alkyl radicals and / or identical or different aryl radicals. The alkyl radicals may each optionally be present as esters, ethers, ether esters and ketones. The aryl radicals may be substituted with aliphatic esters, ethers, ethers and ketones, or present as aromatic esters, ethers, ether esters and ketones.

Particularly preferably, the radicals R ₁ , R ₂ , R ₃ , and R _{4 are} each identical or different acyclic aliphatic radicals, very particularly preferably, these radicals R ₁ , R ₂ , R ₃ , and R _{4 have} one to four carbon atoms. Particularly preferably, the radicals R ₁ , R ₂ , R ₃ , and R _{4 are} methyl radicals.

Preferred zinc-amidine complexes (D) are also those in which the carboxylate radical of the zinc-amidine complex (D) is selected from the group of carboxylate radicals of aliphatic linear and / or branched, optionally substituted monocarboxylic acids 1 to 12 C atoms in the alkyl radical and / or of aromatic, optionally substituted monocarboxylic acids having 6 to 12 C atoms in the aryl radical. The carboxylate radical largely determines the solubility of the resulting complex in the paint components used. Very particular preference is therefore given to using in the coating compositions according to the invention zinc-amidine complexes which are obtainable by reacting 1.0 mol of zinc (II) bis (2-ethylhexanoate) with 3.0 to 4.0 mol of an amidine (I) ,

Particularly preferred are coating compositions containing as component (D) Zn (1,1,3,3-tetramethylguanidine) _x (acetate) ₂ , Zn (1,1,3,3-tetramethylguanidine) _x (formate) ₂ , Zn (1 , 1,3,3-tetramethylguanidine) _x (benzoate) ₂ , Zn (1,1,3,3-tetramethylguanidine) _x (2-ethylhexanoate) ₂ , Zn (1,1,3,3-tetramethylguanidine) _x (octoate ) ₂ , Zn (1,3-diphenylguanidine) _x (formate) ₂ , Zn (1,3-diphenylguanidine) _x (acetate) ₂ , Zn (1,3-diphenylguanidine) _x (benzoate) ₂ , Zn (1.3 Diphenylguanidine) _x (2-ethylhexanoate) ₂ and / or Zn (1,3-diphenylguanidine) _x (octoate) ₂ , preferably Zn (1,1,3,3-tetramethylguanidine) _x (2-ethylhexanoate) ₂ and / or Zn (1,1,3,3-tetramethylguanidine) _x (octoate) ₂ and / or Zn (1,3-diphenylguanidine) _x (2-ethylhexanoate) ₂ and / or Zn (1,3-diphenylguanidine) _x (octoate) ₂ , where in each case x> = 2.5, in particular x = 3.0 to 4.0. Very particularly preferred are coating compositions which contain as component (D) Zn (1, 1,3,3-tetramethylguanidine) _x (2-ethylhexanoate) ₂ and / or Zn (1, 1,3,3-tetramethylguanidine) _x (octoate) ₂ , wherein each x> = 2.5, in particular x = 3.0 to 4.0, is.

The reaction of the zinc or bis (zinc) biscarboxylates with the amidine (s) (I) is usually carried out in a solvent. Suitable solvents here are in particular those solvents which permit a sufficient solubility of the zinc (II) biscarboxylates and the zinc amidines and which are free from isocyanate-reactive groups. Examples of such solvents are the solvents (L) already listed in the polyisocyanate group-containing compound (B).

The reaction of the zinc (II) biscarboxylates with the amidine (s) (I) can also be carried out in the polyhydroxyl-containing component (A) and / or in the low molecular weight alcohols listed as component (C), if appropriate in a mixture with other solvents - such as in particular the just listed solvents (L) - take place.

It is also possible to react the zinc (II) biscarboxylates with the amidine (s) (I) in the overall mixture of the paint component (KI) containing the hydroxyl-containing compounds (A) and, if appropriate, (C) if necessary, the solvent and optionally one or more of the paint additives listed below (F) to perform.

The reaction of the zinc (II) biscarboxylates with the amidine (s) (I) or is usually carried out at room temperature or slightly elevated temperature of up to 100 ° C. As a rule, the zinc (II) biscarboxylate in the solvent or the hydroxyl-containing compound (A) and / or (C) - as just described - submitted and the amidine compound, optionally dissolved in one of the solvents mentioned, slowly added dropwise. The resulting heat is left to cool and then the mixture is stirred for a further 2 hours at at least 60 ° C.

In addition, particularly when the coating compositions are 2-component coating compositions, it is possible to prepare the active catalyst compound (D) in situ. For this purpose, an appropriate amount of the amidine or amidines in the hydroxyl-containing binder (A) and optionally (C) containing paint component (KI) and a corresponding amount of zinc (II) biscarboxylates in the polyisocyanate-containing compound (B) containing Paint component (K-II) solved. When mixing the two paint components prior to application, the zinc-amidine complex is then formed in-situ in the coating composition.

Monomeric aromatic carboxylic acid (S)

It is furthermore essential to the invention that the coating composition contains at least one monomeric, optionally substituted, carboxylic acid (S) whose carboxyl group is conjugated to a π-electron system. The number of carboxyl groups may vary, the carboxylic acids preferably having a carboxyl group. The monomeric aromatic, optionally substituted carboxylic acids preferably have a molecular weight <500 g / mol, more preferably <300 g / mol. Preference is given to using monomeric aromatic, optionally substituted carboxylic acids which have a pKa value of from 2 to 5 exhibit. The pKs value corresponds to the pH at the half-equivalent point, with the dissolution medium preferably being water. If the indication of a pKa value in water is not possible for an acid, it is preferable to use DMSO as the medium or another suitable medium in which the acid is soluble.

Suitable are monomeric aromatic mono- and polycarboxylic acids, the corresponding alkyl and aryl-substituted aromatic mono- and polycarboxylic acids and the corresponding hydroxyl-containing aromatic mono- and polycarboxylic acids such as phthalic acid and terephthalic acid, alkyl- or aryl-substituted phthalic acid and terephthalic acid, benzoic acid and alkyl- or aryl-substituted benzoic acid, aromatic carboxylic acids having further functional groups such as salicylic acid and acetylsalicylic acid, alkyl- or aryl-substituted salicylic acid or isomers thereof, polynuclear aromatic carboxylic acids such as the isomers of naphthalenecarboxylic acid and derivatives thereof.

Preferably, the coating composition contains as monomeric aromatic carboxylic acid (S) benzoic acid, tert-butylbenzoic acid, 3,4-dihydroxybenzoic acid, salicylic acid and / or acetylsalicylic acid, more preferably benzoic acid.

The combination of components (A), (B), optionally (C), (D) and (S) and other components of the coating compositions

When it comes to one-component coating compositions, polyisocyanate-containing compounds (B) are selected whose free isocyanate groups are blocked with blocking agents. For example, the isocyanate groups may be substituted with pyrazoles, especially with alkyl-substituted pyrazoles, such as 3-methylpyrazole, 3,5-dimethylpyrazole, 4-nitro-3,5-dimethypyrazole, 4-bromo-3,5-dimethylpyrazole u. Ä. be blocked. Most preferably, the isocyanate groups of component (B) are blocked with 3,5-dimethylpyrazole.

In the particularly preferred 2-component (2K) coating compositions according to the invention, shortly before the application of the coating composition, a coating component comprising the polyhydroxyl-containing compound (A) and further components described below, with a further coating component containing the polyisocyanate-containing compound (B ) and optionally further of the components described below in a conventional manner, wherein usually the paint component containing the compound (A), the catalyst (D) and a part of the solvent.

The polyhydroxy component (A) may be in a suitable solvent. Suitable solvents are those which allow sufficient solubility of the polyhydroxy component. Examples of such solvents are the solvents (L) already listed in the polyisocyanate group-containing compound (B).

The proportions by weight of the polyol (A) and optionally (C) and the polyisocyanate (B) are preferably selected such that the molar equivalent ratio of the hydroxyl groups of the polyhydroxyl-containing compound (A) plus optionally (C) to the isocyanate groups of the component ( B) is between 1: 0.9 and 1: 1.5, preferably between 1: 0.9 and 1: 1.1, more preferably between 1: 0.95 and 1: 1.05.

According to the invention, preference is given to using coating compositions which contain from 30 to 80% by weight, preferably from 50 to 70% by weight, based in each case on the binder content of the coating composition, at least one polyhydroxyl group-containing Compound (A), in particular at least one polyhydroxyl-containing polyacrylate (A) and / or at least one polyhydroxyl-containing polymethacrylate (A).

Likewise preferred according to the invention are coating compositions which contain from 5 to 50% by weight, preferably from 25 to 40% by weight, based in each case on the binder content of the coating composition, of the polyisocyanate-group-containing compound (B).

The coating compositions according to the invention preferably additionally contain at least one zinc amidine complex (D) in such an amount that the metal content of the zinc amidine complex, based in each case on the binder content of the coating composition, is between 35 and 2000 ppm, preferably between 35 and 1000 ppm and more preferably between 100 and 1000 ppm.

The coating compositions according to the invention preferably also comprise from 0.2 to 15.0% by weight, preferably from 0.5 to 8.0% by weight and more preferably from 0.5 to 5.0% by weight, of at least one aromatic carboxylic acid ( S), wherein the weight percentages are in each case based on the binder content of the coating composition.

Binder content is to be understood as meaning in each case the fraction of the coating composition which is soluble in tetrahydrofuran (THF) before crosslinking. For this purpose, a small sample (P) is weighed, dissolved in the 50 to 100 times the amount of THF, insoluble constituents are filtered off, the THF evaporated and then the solids of the previously dissolved in THF constituents determined by 60 minutes at 130 ° C dried is cooled in a desiccator and then weighed again. The residue corresponds to the binder content of the sample (P).

The coating compositions of the invention are preferably non-aqueous coating agents and may contain solvents or be formulated as solvent-free systems. Examples of suitable solvents are the solvents (L) already listed for the polyhydroxyl-containing compound (A) and, if appropriate, (C) and for the polyisocyanate-containing compound (B). The solvent or solvents are preferably used in the coating compositions according to the invention in an amount such that the solids content of the coating composition is at least 50% by weight, particularly preferably at least 60% by weight.

Furthermore, the coating compositions according to the invention 0 to 30 wt .-%, preferably 0 to 15 wt .-%, each based on the binder content of the coating composition, one or more aminoplast resins and / or one or more tris (alkoxycarbonylamino) triazines (E) included.

Examples of suitable tris (alkoxycarbonylamino) triazines are in the US-A-4,939,213 , of the US-A-5 084 541 and the EP-A-0 624 577 called.

Examples of suitable aminoplast resins (E) are all amino resins conventionally used in the paint industry, wherein the properties of the resulting coating compositions can be controlled by the reactivity of the aminoplast resin. These are condensation products of aldehydes, in particular formaldehyde, and for example urea, melamine, guanamine and benzoguanamine. The aminoplast resins contain alcohol, preferably methylol, which as a rule partially or preferably completely etherified with alcohols are. In particular, etherified amino resins are used with lower alcohols. Preference is given to using aminoplast resins etherified with methanol and / or ethanol and / or butanol, for example products available commercially under the names Cymel®, Resimene®, Maprenal® and Luwipal®.

The aminoplast resins (E) are well-known compounds and are described, for example, in detail in the American patent application US 2005/0182189 A1 , Page 1, paragraph [0014], to page 4, paragraph [0028].

In addition, the binder mixture or the coating composition of the invention may contain at least one customary and known coating additive (F) in effective amounts, i. in amounts preferably up to 30% by weight, more preferably up to 25% by weight and in particular up to 20% by weight, based in each case on the binder content of the coating composition.

• insbesondere UV-Absorber;
• insbesondere Lichtschutzmittel wie HALS-Verbindungen, Benztriazole oder Oxalanilide;
• Radikalfänger;
• Slipadditive;
• Polymerisationsinhibitoren;
• Entschäumer;
• von den Komponenten (A) und (C) verschiedene Reaktivverdünner, insbesondere Reaktivverdünner, die erst durch Reaktion mit weiteren Bestandteilen bzw. Wasser reaktiv werden, wie beispielsweise Incozol® oder Asparaginsäureester
• von den Komponenten (A) und (C) verschiedene Netzmittel wie Siloxane, fluorhaltige Verbindungen, Carbonsäurehalbester, Phosphorsäureester, Polyacrylsäuren und deren Copolymere oder Polyurethane;
• Haftvermittler;
• Verlaufsmittel;
• filmbildende Hilfsmittel wie Cellulose-Derivate;
• Füllstoffe wie beispielsweise Nanopartikel auf der Basis von Siliziumdioxid, Aluminiumoxid oder Zirkoniumoxid; ergänzend wird noch auf das Römpp Lexikon »Lacke und Druckfarben« Georg Thieme Verlag, Stuttgart, 1998, Seiten 250 bis 252 , verwiesen;
• von den Komponenten (A) und (C) verschiedene rheologiesteuernde Additive, wie die aus den Patentschriften WO 94/22968 , EP-A-0 276 501 , EP-A-0 249 201 oder WO 97/12945 bekannten Additive; vernetzte polymere Mikroteilchen, wie sie beispielsweise in der EP-A-0 008 127 offenbart sind; anorganische Schichtsilikate wie Aluminium-Magnesium-Silikate, Natrium-Magnesium- und Natrium-Magnesium-Fluor-Lithium-Schichtsilikate des Montmorillonit-Typs; Kieselsäuren wie Aerosile®; oder synthetische Polymere mit ionischen und/oder assoziativ wirkenden Gruppen wie Poly(meth)acrylamid, Poly(meth)acrylsäure, Polyvinylpyrrolidon, Styrol-Maleinsäureanhydrid- oder Ethylen-Maleinsäure-anhydrid-Copolymere und ihre Derivate oder hydrophob modifizierte ethoxylierte Urethane oder Polyacrylate;
• Flammschutzmittel.

Examples of suitable paint additives (F) are:

• in particular UV absorber;
• in particular light stabilizers such as HALS compounds, benzotriazoles or oxalanilides;
• Radical scavengers;
• slip additives;
• polymerization inhibitors;
• defoamers;
• reactive diluents which are different from components (A) and (C), in particular reactive diluents, which become reactive only by reaction with further constituents or water, for example Incozol® or aspartic acid esters
• wetting agents other than components (A) and (C), such as siloxanes, fluorine-containing compounds, carboxylic acid monoesters, phosphoric esters, polyacrylic acids and their copolymers or polyurethanes;
• Adhesion promoters;
• Leveling agents;
• film-forming aids such as cellulose derivatives;
• Fillers such as nanoparticles based on silica, alumina or zirconia; in addition, the Römpp Lexikon »Paints and Printing Inks« Georg Thieme Verlag, Stuttgart, 1998, pages 250 to 252 , directed;
• from the components (A) and (C) different rheology control additives, such as those from Patents WO 94/22968 . EP-A-0 276 501 . EP-A-0 249 201 or WO 97/12945 known additives; crosslinked polymeric microparticles, as described for example in the EP-A-0 008 127 are disclosed; inorganic phyllosilicates such as aluminum-magnesium silicates, sodium magnesium and sodium magnesium fluorine lithium phyllosilicates of the montmorillonite type; Silicas such as Aerosile®; or synthetic polymers having ionic and / or associative groups such as poly (meth) acrylamide, poly (meth) acrylic acid, polyvinylpyrrolidone, styrene-maleic anhydride or ethylene-maleic anhydride copolymers and their derivatives or hydrophobically modified ethoxylated urethanes or polyacrylates;
• Flame retardants.

Particular preference is given to coating compositions which contain from 50 to 70% by weight, based on the binder content of the coating composition, of at least one polyhydroxyl-containing polyacrylate (A) and / or at least one polyhydroxyl-containing polymethacrylate (A),
From 25 to 40% by weight, based on the binder content of the coating composition, of the polyisocyanate group-containing compound (B)
0 to 10 wt .-%, based on the binder content of the coating composition, the hydroxyl-containing component (C) 0.5 to 5.0 wt .-%, based on the binder content of the coating composition, at least one aromatic carboxylic acid (S)
0 to 15 wt .-%, based on the binder content of the coating composition, of one or more aminoplast resins and / or one or more tris (alkoxycarbonylamino) triazines (E) and
0 to 20 wt .-%, based on the binder content of the coating composition, at least one conventional and known paint additive (F) and
contain at least one zinc amidine complex (D) in such an amount that the metal content of the zinc-amidine complex, based in each case on the binder content of the coating composition, between 100 and 1000 ppm.

In a further embodiment of the invention, the binder mixture according to the invention or the coating composition according to the invention may contain further pigments and / or fillers and for the production of pigmented topcoats or pigmented undercoats or fillers, in particular pigmented topcoats. The pigments and / or fillers used for this purpose are known to the person skilled in the art. The pigments are usually employed in an amount such that the pigment-to-binder ratio is between 0.05: 1 and 1.5: 1, in each case based on the binder content of the coating composition.

Since the coatings according to the invention prepared from the coating compositions according to the invention are also outstandingly well-adhered to already cured electrocoats, surfacers, basecoats or customary and known clearcoats, they are excellently suitable for automotive refinishing and / or for use in automotive series (OEM) painting Coating of automotive components and / or the coating of commercial vehicles.

The application of the coating compositions according to the invention can be carried out by all customary application methods, such as e.g. Spraying, knife coating, brushing, pouring, dipping, watering, trickling or rolling done. In this case, the substrate to be coated can rest as such, with the application device or system being moved. However, the substrate to be coated, in particular a coil, can also be moved, with the application system resting relative to the substrate or being moved in a suitable manner.

Preferably, spray application methods are used, such as compressed air spraying, airless spraying, high rotation, electrostatic spray application (ESTA), optionally combined with hot spray application such as hot air hot spraying.

The curing of the applied coating compositions according to the invention can take place after a certain rest period. The rest period serves, for example, for the course and degassing of the paint layers or for the evaporation of volatile components such as solvents. The rest period can be supported and / or shortened by the application of elevated temperatures and / or by a reduced air humidity, provided that no damage or changes in the paint layers occur, such as premature complete crosslinking.

The thermal curing of the coating compositions has no special features, but is carried out by the usual and known methods such as heating in a convection oven or irradiation with IR lamps. Here, the thermal curing can also be done gradually. Another preferred curing method is near infrared (NIR) curing.

Advantageously, the thermal curing is carried out at a temperature of 20 to 200 ° C for a period of 1 min to 10 h, with longer curing times can be used at low temperatures. For automotive refinishing and for the coating of plastic parts and the painting of commercial vehicles usually lower temperatures are applied, which are preferably between 20 and 80 ° C, in particular between 20 and 60 ° C.

The coating compositions according to the invention are outstandingly suitable as decorative, protective and / or effect, coatings and coatings of bodies of vehicles (especially motor vehicles, such as bicycles, motorcycles, buses, trucks or cars) or parts thereof; of buildings in the interior and exterior; of furniture, windows and doors; of plastic moldings, in particular CDs and windows; of industrial small parts, of coils, containers and packaging; of white goods; of films; of optical, electrotechnical and mechanical components as well as glass hollow bodies and everyday objects.

The coating compositions according to the invention can therefore be applied, for example, to an optionally precoated substrate, it being possible for the coating compositions according to the invention to be both pigmented and unpigmented. In particular, the Coating compositions and coatings according to the invention, in particular the clearcoats, in the technologically and aesthetically particularly demanding field of automotive OEM (OEM) and for coating of plastic add-on parts for car bodies, especially for bodies of cars of the upper class, such. As for the production of roofs, tailgates, hoods, fenders, bumpers, spoilers, sills, protective strips, side panels u.Ä., And the automotive refinishing and painting of commercial vehicles, such as trucks, chain-driven construction vehicles, such as crane vehicles, Wheel loaders and concrete mixers, buses, rail vehicles, watercraft, aircraft and agricultural equipment such as tractors and combines, and parts thereof.

The plastic parts usually consist of ASA, polycarbonates, blends of ASA and polycarbonates, polypropylene, polymethyl methacrylates or impact-modified polymethylmethacrylates, in particular blends of ASA and polycarbonates, preferably with a polycarbonate content> 40%, in particular> 50%.

ASA is generally understood to mean impact-modified styrene / acrylonitrile polymers in which graft copolymers of vinylaromatic compounds, in particular styrene, and of vinyl cyanides, in particular acrylonitrile, are present on polyalkyl acrylate rubbers in a copolymer matrix of, in particular, styrene and acrylonitrile.

The coating compositions according to the invention are particularly preferably used in multi-stage coating processes, in particular in processes in which an optionally precoated substrate is first of all pigmented basecoat and then a coating of the coating composition of the invention be applied. The invention therefore also relates to effect and / or coloring multicoat paint systems comprising at least one pigmented basecoat film and at least one clearcoat film disposed thereon, which are characterized in that the clearcoat film has been prepared from the coating composition of the invention.

Both waterborne basecoats and basecoats based on organic solvents can be used. Suitable basecoats are for example in the EP-A-0 692 007 and in those in column 3, lines 50ff. described documents. Preferably, the applied basecoat is first dried, that is, the basecoat film is removed in an evaporation phase, at least a portion of the organic solvent or of the water. The drying is preferably carried out at temperatures from room temperature to 80 ° C. After drying, the coating composition of the invention is applied. Subsequently, the two-coat finish is preferably baked under conditions used in automotive OEM finishing at temperatures of 20 to 200 ° C for a period of 1 min to 10 h, wherein at the applied temperatures for the automotive refinishing, generally between 20 and 80 ° C, especially between 20 and 60 ° C, even longer curing times can be used.

In a further preferred embodiment of the invention, the coating composition according to the invention is used as a transparent clearcoat for coating plastic substrates, in particular plastic attachment parts. The plastic attachment parts are preferably also coated in a multi-stage coating process, in which an optionally precoated or pretreated for better adhesion of the subsequent coatings Substrate (eg flaming, corona or plasma treatment of the substrate) first a pigmented basecoat layer and then a layer with the coating composition of the invention are applied.

Examples Gel permeation chromatography (GPC)

Gel permeation chromatography was performed at 40 ° C with a high performance liquid chromatography pump and a refractive index detector. As the eluent, tetrahydrofuran was used at an elution rate of 1 mL / min. The calibration was carried out using polystyrene standards. The number average molecular weight Mn, the weight average molecular weight Mw and Mp were determined, and the polymolecular index Mp calculated from Mp = Mw / Mn.

hydroxyl

The hydroxyl number is calculated via the proportion of OH-functional components used and stated in mg KOH per gram of solid resin.

Solid determination

Approximately 1 g sample is weighed in a tinplate lid. After addition of about 3 ml of butyl acetate, the sample is dried in a drying oven for 60 minutes at 130 ° C, cooled in a desiccator, and then weighed back. The residue corresponds to the solids content.

Binder content determination

Binder content is to be understood as meaning in each case the fraction of the coating composition which is soluble in tetrahydrofuran (THF) before crosslinking. For this a small sample (P) is weighed, in the 50 to 100-fold Dissolved amount of THF, insoluble constituents are filtered off, the THF evaporated and then the solids of previously dissolved in THF constituents determined by drying for 60 minutes at 130 ° C, cooled in a desiccator and then weighed again. The residue corresponds to the binder content of the sample (P).

Tack free with Zapon-Tack Test (ZTT):

An aluminum strip with a thickness of about 0.5 mm, a width of 2.5 cm and a length of about 11 cm is bent at a 110 ° angle so that an area of 2.5 X 2.5 cm is formed , The long side of the sheet is bent after another 2.5 cm by about 15 ° so that the sheet is kept in balance by a centered on the square surface placed weight of 5 g. To measure the freedom from tack after ZTT the bent sheet metal is placed on the paint film and weighted for 30 s with a weight of 100g. After removal of the weight of the paint is considered tack-free, if the sheet metal angle falls within 5 s. The test is repeated every 15 minutes. Before using the test, the tackiness of the paint film is qualitatively assessed by touch. For elevated temperature tests, the test panels are stored at room temperature for 10 minutes prior to the cooling test.

Print test:

The paint film is mounted on a glass sheet by means of a 100 μm doctor blade. After drying for 15 minutes at 60 ° C, the glass sheet is placed on a commercial laboratory balance within 10 minutes after removal from the oven. By means of thumb pressure, the film is then loaded for 20 s with a weight of 2 kg. This test is repeated every 10 minutes. In apparently still soft or sticky paint film is first waited until the paint film has reached a sufficient freedom from tack and hardness. The evaluation of the tests is after a storage period made by 24 hours. For this purpose, the paint surface is washed off with an aqueous surfactant solution (commercially available washing-up liquid) and a soft cloth in order to eliminate grease markings. It is always measured against a standard. The paint is considered ok if no thumbprint is visible on the paint film. This test is a measure of the installation resistance of refinish coatings, ie the sooner the paint film has reached its mounting strength after forced drying, the sooner assembly work (or disassembly work on the repaired bodywork) can be started.

Drying recorder:

On glass panels measuring 280 mm x 25 mm, the paint is applied using a 100μ box doctor. With the help of the Byk-Dry-Time recorder, at room temperature (20 - 23 ° C) and a relative humidity of 40 to 60%, needles are pulled over the film at a defined speed. Here, 3 different phases as well as the total length (= sum of phase 1 + phase 2 + phase 3) of the lane are assessed.
Phase 1: The needle track starts to close again
Phase 2: The needle track leads to a deep furrow in the paint film Phase 3: The needle injures the film only superficially
The assessment is always against a standard.

pot life:

For this, the viscosity is measured at room temperature of a paint sample in the DIN4 flow cup. Beforehand, the sample is adjusted to an outlet viscosity of 19 - 20 seconds in the DIN4 cup. Thereafter, the viscosity increase is determined at suitable intervals. Once the sample has doubled its initial viscosity, the potlife limit is reached.

Pendulum hardness:

The hardness of the paint films is determined by means of pendulum damping Koenig according to DIN 53157. Indicated are the pendulum strokes.

Master batch:

86.4 g of a styrene-containing polyacrylate (62% in Solventnaptha® / ethoxyethyl propionate / methyl isobutyl ketone (20/46/34)) having a molecular weight of 1600-2200 (Mn) and 4000-5000 (Mw), a measured acid number of 12-16 mg KOH / g, a calculated OH number (OHN) of about 130 mg KOH / g (solid resin) and a viscosity of the 60% solution in butyl acetate of 200-400 mPa.s, measured with a rotational viscometer (Brookfield CAP 2000, Spindle 3, 1000RPM), are stirred with 6.4 g of methyl isobutyl ketone, 2.2 g of a commercial light stabilizer mixture consisting of UV and HALS light stabilizer and 0.15 g of a commercial leveling agent based on a polyacrylate to form a homogeneous mixture. To this mixture, if indicated, the corresponding catalyst is added with stirring. When benzoic acid is used, it is dissolved with stirring as a solid in the stock paint mixture. To adjust the viscosity, another 1.0 part of methylsobutyl ketone and 2.80 parts of butyl acetate are added.

Hardener solution:

In a mixture of 5.17 parts of xylene, 7.48 parts of butyl acetate, 1.506 parts of ethyl ethoxypropionate, 7.03 parts of methyl isobutyl ketone and 0.3 parts of a commercial leveling agent based on a polyacrylate (55% in Solventnaphtha®) are 28.1 g trimerized, containing isocyanurate hexamethylene diisocyanate (HDI) having an isocyanate content of 22.0%, based on the solvent-free trimerized hexamethylene diisocyanate, dissolved.

catalysts: Catalyst K2

48.34 g of zinc (II) bis (2-ethylhexanoate) (0.137 mol) are dissolved in 20 g of butyl acetate. To this is slowly added dropwise 31.656 g of 1,1,3,3-tetramethylguanidine (0.275 mol). After the exothermic reaction has subsided, stirring is continued at RT ° C. for a further 20 minutes.

Catalyst K3

40.36 g of zinc (II) bis (2-ethylhexanoate) (0.115 mol) are dissolved in 20.0 g of butyl acetate. 39.64 g of 1,1,3,3-tetramethylguanidine (0.344 mol) are slowly added dropwise thereto. After the exothermic reaction has subsided, stirring is continued at RT ° C. for a further 20 minutes.

Catalyst K4

34.64 g of zinc (II) bis (2-ethylhexanoate) (0.1 mol) are dissolved in 20.0 g of butyl acetate. 45.36 g of 1,1,3,3-tetramethylguanidine (0.4 mol) are slowly added dropwise thereto. After the exothermic reaction has subsided, stirring is continued at RT ° C. for a further 20 minutes.

Experimental procedure:

Additional components such as benzoic acid and catalyst solutions are dissolved in the master paint. After gentle stirring gives clear solutions.
To carry out the experiment, the stock paint is initially charged and the hardener is added. The solution is homogenized by stirring.
For the viscosity measurements, the viscosity is adjusted to the specified viscosity by addition of solvent.
For the glass elevators omitted the adjustment of the viscosity.
For the drying test, the paint film is applied to glass panels by means of a 100 μm box doctor blade, so that a film layer thickness of 30-35 μm is achieved. For the pendulum hardness test, the film is placed on glass panels before the film hardness is determined by Koenig, the layer thickness of the coated film at the scribe (DIN 50933) is determined. For the tests by means of the Drying Recorder, the samples are also mounted with a 100 μm box doctor blade on suitable glass strips of approx. 300 mm length and approx. 25 mm width; the resulting layer thicknesses are 30-35 μm.

Examples 1 and 2 and Comparative Examples V1 and V2

First, the coating compositions of Examples 1 and 2 were prepared with various zinc-amidine complexes but with equal amounts of benzoic acid. In addition, in Comparative Examples C1 and C2, the corresponding coating agents were prepared without benzoic acid. The composition of these coating agents of Examples 1 and 2 and Comparative Examples V1 and V2 and the test results of the resulting coatings are shown in Table 1. Table 1: Composition of the coating compositions of Examples 1 and 2 and Comparative Examples V1 and V2 and the test results of the resulting coatings E1 E2 V1 V2 stock paint 98.97 98.97 98.97 98.97 benzoic acid 2.43 2.43 Catalyst K3 0.3 0.3 Catalyst K4 0.35 0.35 hardener solution 49.85 49.85 49.85 49.85 Metal content ¹⁾ [ppm] 275 275 275 275 Potlife DIN 4 [s] ²⁾ directly 19 19 21 21 after 1h 24 25 25 25 after 2h 33 36 33 35 after 3h 54 63 39 42 ZAPON-Tack 30 '60 ° C / 10'RT [min] ³⁾ 1 1 265 310 23 ° C RT [min] 380 380 480 480 sway 23 ° C RT after 1d ⁴⁾ 95 83 72 72 23 ° C RT after 7d ⁴⁾ 133 117 135 137 30'60 ° C after 1d ⁵⁾ 96 113 94 98 30'60 ° C after 7d ⁵⁾ 141 144 146 147 Drying Recorder ⁶⁾ Total length of scratch track [cm] 17.8 12.5 24.7 25 Phase 1 [cm] 6.7 5 6.5 6.5 Phase 2 [cm] 7.9 4.9 10.8 11.8 Phase 3 [cm] 3.2 2.6 7.4 6.7 Print - Test - 15 min 60 ° C ⁷⁾ [min] 60 40 280 260 Explanatory notes to Table 1
¹⁾ is the amount of catalyst K3 or K4 in ppm metal content, based on the binder content of the coating composition
^{2) the} viscosity of the coating composition measured in the DIN4 flow cup at room temperature is measured directly after preparation and after 1, 2 and 3 hours after its preparation
³⁾ Measurement of tack freedom with the Zapon-Tack test after curing the coating for 30 minutes at 60 ° C and commencing the test after storage of the panels for 10 minutes at room temperature and measuring the tack-freeness with the Zapon-Tack test while preserving the coating room temperature
⁴⁾ Measurement of pendulum hardness after storage of the coating 1 or 7 days at room temperature
⁵⁾ Measurement of pendulum hardness after curing of the coating for 30 min at 60 ° C and subsequent storage of the coating 1 or 7 days at room temperature
⁶⁾ , the total length of the scratching track in cm and the length of the scratching track in cm are in each case according to phases 1, 2 and 3
⁷⁾ is the time in minutes after which the impression in the print test after drying for 15 min 60 ° C and subsequent storage of the panels for 10 minutes at room temperature is no longer visible

Discussion of the test results

The comparison of Examples 1 and 2 with the corresponding Comparative Examples V1 and V2 shows that the coating compositions according to the invention are characterized by rapid curing even under the conditions of refinishing and thus a good mounting strength after a very short time, without thereby Potlife seriously negative being affected. Usually, a prolonged potlife with a worse, i. slower curing and thus good mounting strength only after much longer time, bought. Finally, the curing of the coating compositions according to the invention, especially at room temperature drying, is faster than the curing of the coating compositions without benzoic acid, as the comparison of the results of the Drying Recorder for Examples 1 and 2 with Comparative Examples V1 and V2 shows. The higher reactivity is also reflected in the hardness development, determined by the pendulum hardness.

Furthermore, the coating composition of Comparative Example V3 was analogous to WO06 / 022899 prepared with the Zn (1,1,3,3-tetramethylguanidine) ₂ (2-ethylhexanoate) ₂ complex and without aromatic carboxylic acid. In Comparative Example C4, finally, a coating composition based on tin-containing catalysts was prepared. The composition The coating compositions of Comparative Examples V3 and V4 and the test results of the resulting coatings are shown in Table 2. Table 2: Composition of the coating compositions of Comparative Examples V3 and V4 in parts by weight and the test results of the resulting coatings example V3 V4 stock paint 98.97 98.97 benzoic acid 1.5 Catalyst K2 0,250 dibutyltindilaurate 0.06 hardener solution 49.58 49.58 Metal content ¹⁾ [ppm] 275 140 test results V3 V4 Potlife DIN 4 [s] ²⁾ directly 21 19 after 1h 26 23 after 2h 30 36 after 3h 39 78 Drying Recorder ³⁾ Total length [cm] 25.2 17.2 Phase 1 [cm] 6.9 4.4 Phase 2 [cm] 11.2 6.5 Phase 3 [cm] 7.1 6.3 Print - Test - 15 min 60 ° C / 10 min RT ⁷⁾ [min] 340 80 Explanatory notes to Table 2:
¹⁾ is the amount of catalyst K2 in ppm metal content, based on the binder content of the coating composition
^{2) the} viscosity of the coating composition measured in the DIN4 flow cup at room temperature is measured directly after preparation and after 1, 2 and 3 hours after its preparation
³⁾ the total length of the scratching track in cm and the length of the scratching track in cm are indicated in each case after phase 1, 2 and 3
⁴⁾ is the time in minutes, after which the impression in the print test after drying for 15 min 60 ° C and subsequent storage of the panels for 10 minutes at room temperature is no longer visible

Discussion of the test results

As the results of the print test of Comparative Example V3 show, the coating compositions have the same properties as those of the WO06 / 022899 (So based on the Zn (1,1,3,3-tetramethylguanidine) ₂ (2-ethylhexanoate) ₂ complex and without the addition of benzoic acid) insufficient curing under the conditions of the refinish and thus insufficient mounting strength. Comparison of Examples 1 and 2 with Comparative Example C4 shows that the coating compositions according to the invention have a significantly improved, ie longer, pot life than the conventional coating compositions based on tin-containing catalysts.

Claims (16)

1. Coating material composition comprising at least one polyhydroxyl group-containing compound (A), at least one polyisocyanate group-containing compound (B) having free and/or blocked isocyanate groups, at least one catalyst (D) based on a zinc-amidine complex which is preparable by reaction of 1.0 moles of one or more zinc(II) biscarboxylates with more than 2.0 moles of an amidine of the formula (I) or with more than 2.0 moles of a mixture of two or more amidines of the formula (I)

   

   where R₅ = hydrogen and R₁, R₂, R₃, and R₄ are each identical or different radicals, R₁ and R₃ being hydrogen or an alkyl radical or an aryl radical, and R₂ and R₄ being an alkyl radical or an aryl radical,
   and at least one monomeric aromatic, optionally substituted carboxylic acid (S) whose carboxyl group is in conjugation with a π-electron system.
2. Coating material composition according to Claim 1, characterized in that the radicals R₂ and R₄ are identical or different acyclic, straight-chain or branched alkyl radicals and/or identical or different aryl radicals, and also the radicals R₁ and R₃ are hydrogen or identical or different acyclic, straight-chain or branched alkyl radicals and/or identical or different aryl radicals, preferably in that the radicals R₁, R₂, R₃, and R₄ are acyclic aliphatic alkyl radicals, more preferably acyclic aliphatic alkyl radicals having 1 to 4 carbon atoms, and very preferably methyl radicals.
3. Coating material composition according to Claim 1 or 2, characterized in that the zinc-amidine complex is alternatively preparable by reaction of 1.0 moles of one or more of zinc(II)biscarboxylates with at least 2.5, more preferably with at least 3.0, and very preferably with 3.0 to 4.0 moles of one or more amidines of the formula (I).
4. Coating material composition according to any of Claims 1 to 3, characterized in that the carboxylate radical of the zinc-amidine complex (D) is selected from the group of the carboxylate radicals of aliphatic linear and/or branched, optionally substituted monocarboxylic acids having 1 to 12 C atoms in the alkyl radical and/or of aromatic, optionally substituted monocarboxylic acids having 6 to 12 C atoms in the aryl radical.
5. Coating material composition according to any of Claims 1 to 4, characterized in that the coating material composition comprises as component (D) Zn(1,1,3,3-tetramethylguanidine)_x(acetate)₂, Zn(1,1,3,3-tetramethylguanidine)_x(formate)₂, Zn(1,1,3,3-tetramethylguanidine)_x(benzoate)₂, Zn(1,1,3,3-tetramethylguanidine)_x(2-ethylhexanoate)₂, Zn(1,1,3,3-tetramethyl-guanidine)_x(octoate)₂, Zn(1,3-diphenylguanidine)_x(formate)₂, Zn(1,3-diphenylguanidine)_x(acetate)₂, Zn(1,3-diphenylguanidine)_x(benzoate)₂, Zn(1,3-diphenylguanidine)_x(2-ethylhexanoate)₂, and/or Zn(1,3-diphenylguanidine)_x(octoate)₂, with x, in each case, being greater than or equal to 2.5, in particular x = 3.0 to 4.0 and preferably as component (D) Zn(1,1,3,3-tetramethylguanidine)_x(2-ethylhexanoate)₂ and/or Zn(1,1,3,3-tetramethylguanidine)_x(octoate)₂ and/or Zn(1,3-diphenylguanidine)_x(2-ethylhexanoate)₂ and/or Zn(1,3-diphenylguanidine)_x(octoate)₂ with x, in each case, being greater than or equal to 2.5, in particular x = 3.0 to 4.0.
6. Coating material composition according to any of Claims 1 to 5, characterized in that the coating material composition comprises as carboxylic acid (S) benzoic acid, tert-butylbenzoic acid, 3,4-dihydroxybenzoic acid, salicylic acid and/or acetylsalicylic acid, preferably benzoic acid.
7. Coating material composition according to any of Claims 1 to 6, characterized in that the coating material composition comprises at least one zincamidine complex (D) in an amount such that the metal content of the zinc-amidine complex, based in each case on the binder fraction of the coating material composition, is between 35 and 2000 ppm, preferably between 35 and 1000 ppm, and more preferably between 100 and 1000 ppm, and/or the coating material composition comprises 0.2% to 15.0% by weight, preferably 0.5% to 8.0% by weight, and more preferably 0.5% to 5.0% by weight, of at least one aromatic carboxylic acid (S), the percentages by weight in turn being based in each case on the binder fraction of the coating material composition.
8. Coating material composition according to any of Claims 1 to 7, characterized in that the coating material composition comprises as component (B) at least one compound having free isocyanate groups and/or in that it comprises as component (B) 1,6-hexamethylene diisocyanate, isophorone diisocyanate, or 4,4'-methylenedicyclohexyl diisocyanate, the biuret dimers of the aforementioned diisocyanates and/or the isocyanurate trimers of the aforementioned diisocyanates and/or the asymmetric trimers of the aforementioned diisocyanates.
9. Coating material composition according to any of Claims 1 to 8, characterized in that the polyhydroxyl group-containing compound (A) is selected from the group of the polyacrylate polyols, the polymethacrylate polyols, the polyester polyols, the polyurethane polyols and/or the polysiloxane polyols, more particularly from the group of the polyacrylate polyols and/or the polymethacrylate polyols.
10. Coating material composition according to any of Claims 1 to 9, characterized in that the coating material composition further comprises one or more hydroxyl-containing compounds (C) different from component (A), and/or in that the molar equivalents ratio of the hydroxyl groups in the hydroxyl-containnig compound (A) plus optionally (C) to the isocyanate groups of component (B) is between 1:0.9 and 1:1.5, preferably between 1:0.9 and 1:1.1, more preferably between 1:0.95 and 1:1.05.
11. Coating material composition according to any of Claims 1 to 10, characterized in that it is a nonaqueous coating material composition and/or in that it comprises pigments.
12. Multistage coating method characterized in that an optionally precoated substrate has applied to it a pigmented basecoat film and thereafter a film of the coating material composition according to any of Claims 1 to 11, or in that an optionally precoated substrate has applied to it a pigmented or unpigmented film of the coating material composition according to any of Claims 1 to 11.
13. Multistage coating method according to Claim 12, characterized in that application of the pigmented basecoat film is followed first by drying of the applied basecoat material at temperatures from room temperature to 80°C, and the application of the coating material composition according to any of Claims 1 to 11 is followed by curing at temperatures between 20 and 80°C, more particularly between 20 and 60°C.
14. Use of the coating material compositions according to any of Claims 1 to 11 as clearcoat material or pigmented coating material for automotive refinish and/or for the coating of parts for installation in or on automobiles, and/or of plastics substrates and/or of utility vehicles.
15. Application of the method according to Claim 12 or 13 for automotive refinish and/or for the coating of plastics substrates and/or of utility vehicles.
16. Use of at least one zinc-amidine complex (D) which is preparable by reaction of 1.0 moles of one or more zinc(II) biscarboxylates with more than 2.0 moles of one or more amidines of the formula (I), and at least one monomeric aromatic carboxylic acid (S) whose carboxyl group is in conjugation with a □-electron system, as a catalyst system for catalysis of the urethane reaction in coating material compositions which comprise at least one polyisocyanate group-containing component and at least one polyhydroxyl group-containing component.